There is conventionally known a sheet feeder provided with a mechanism for separating one sheet from a plurality of stacked sheets and conveying the separated sheet. This conventional sheet feeder comprises a first roller, a second roller, and a pick arm. When a plurality of sheets is stacked on a shooter, the first roller conveys the bottommost sheet downstream in a conveying direction. The second roller restrains sheets other than the bottommost sheet from being conveyed downstream. The pick arm can move in a direction toward the first roller and a direction away from the first roller. The pick arm rotatably supports a third roller at a portion of the pick arm positioned nearest the first roller. A spring urges the pick arm toward the first roller. The third roller contacts the topmost sheet of the stacked sheets when the pick arm is moved toward the first roller by the urging force of the spring. In this case, the third roller presses the bottommost sheet against the first roller.